Rupturing Farallon slab formed Columbia River flood basalt

[Liu & Stegman, Nature 2012]

15 Ma0 Ma

Geometry of the subducting

Farallon slab and mantle flow

Geometry of the subducting

Farallon slab and mantle flow

The slab tear causing CRB is

now imaged by tomography

The slab tear causing CRB is

now imaged by tomography

• Modeling western US seismic structure requires the Farallon slab to break ~16 Ma, and the slab tearing coincides with the sequence of CRB eruptions both in space and time (upper right).

• The slab tear involves a focused asthenosphere upwelling (lower right), suggesting that the CRB magmas are from re-melting of the subducting oceanic lithosphere and oceanic crust.